Autocatalysis occurs in a (chemical) reaction, if the reaction product itself catalyzes further reactions. It is a form of catalysis in which one of the products of a reaction serves as a catalyst for the reaction. In chemistry and biology, catalysis is the acceleration the reaction rate of a chemical reaction by means of a substance, called a catalyst or enzyme (in biology). A catalyst accelerates, facilitates and enhances a bio-chemical reation. Nearly all biochemical processes are catalyzed by enzymes.
Autocatalysis describes a self-enhancing and self-amplifying reaction, and is a special form of positive feedback. An example of autocatalysis is the hypercycle, in which self-replicating entities or reations catalyze each other. M. Eigen and P. Schuster proposed the model of hypercycles to explain the origin of the DNA through self-replicating molecules.
Manfred Eigen and Peter Schuster, The Hypercycle: A Principle of Natural Self Organization, Springer-Verlag 1979, ISBN 0387092935